Some degree of memory loss is a normal part of the aging process. Mild cognitive impairment, on the other hand, is associated with one or more abnormalities on neuropsychological testing, and may represent the earliest stage of Alzheimer’s disease.
What’s normal? Memory changes occur as part of normal aging, and generally occur after the age of 40. This type of memory loss is not progressive. In other words, it doesn’t get worse over time. In addition, there is no change in day-to-day functional ability. There may be an occasional short-term memory lapse: you may forget where you put your car keys, or the name of a person you have not seen in six months who is an occasional acquaintance. This kind of memory change is not considered abnormal. Normal, age-related memory loss is compatible with a productive and independent life. And remember, a lot of “memory loss” can be attributed to not paying attention. We live in a society with lots of multitasking, which is associated with a decreased ability to pay close attention and focus. High quality memory is not created when we are inattentive.
What are the earliest signs of Alzheimer’s disease, and how do we detect them? We now believe that there is a clinical spectrum of Alzheimer’s disease that begins 20-25 years before there are any symptoms of memory loss, and this spectrum includes pre-clinical Alzheimer’s disease, mild cognitive impairment, and finally dementia due to Alzheimer’s disease. We can now detect the pathologic changes in the brain (for example an abnormal protein called “amyloid beta peptide” or “Abeta42”) before there are any clinical symptoms. Using biomarkers (such as examination of cerebral spinal fluid; or a type of brain imaging called PET scanning), we are able to visualize or detect abnormal amounts of Abeta42 in the brain of someone who is 55 years old who will not develop symptoms of Alzheimer’s disease until the age of 70. In other words, there appears to be a long period of accumulating pathology before there is enough damage to the brain to cause the symptoms of Alzheimer’s disease.
There is an interesting caveat to this scenario, which is that some brains tolerate this abnormal protein with no change in cognitive abilities. That is to say in some people, biomarkers indicate the presence of Abeta 42, yet they never develop any symptoms of Alzheimer’s disease. That’s why clinical evaluation and testing remains critically important.
How do we test a person who may be experiencing memory symptoms? We perform neuropsychologic testing to evaluate performance in multiple cognitive domains of the brain: memory, language, visuospatial function, attention and concentration, orientation, and executive function. Executive function refers to frontal lobe activity that engages in planning and decision-making, like planning the preparation of a meal. We collect a clinical history from the patient and from an outside, objective observer to determine what kind of symptoms a person has been experiencing to suggest that they may be developing Alzheimer’s disease. If neuropsycologic testing and the clinical history are discordant, we always defer to the clinical history. However, most often these two aspects of the clinical evaluation match well, and indicate that the patient is either normal or developing Alzheimer’s disease.
What are some lifestyle strategies that reduce the risk for cognitive impairment? Regular intellectual activity, like learning a new language, is really good for the brain, as are word games and computer-based exercises. Regular physical exercise, such as an aerobic walk three times per week, is also important. Finally, social integration is crucial. There is evidenced based correlation between loneliness and the development of dementia.
William W. Pendlebury, MD, is Medical Director of the Memory Center at the University of Vermont Medical Center and Professor at the Larner College of Medicine at UVM. His areas of expertise include Alzheimer’s disease and related disorders, geriatric medicine and neuropathology.